"Donald is going to be as serious as Donald wants to be. And he's going to determine through the depth of his answers and the seriousness of his answers whether he is a serious candidate or he isn't," Christie said in an interview with CNN's Jake Tapper aired Sunday on "State of the Union."

"Anybody can do well for a month in this business, especially if you have talent and personality, and Donald has both those things. Let's see how this goes over the course of time," he said.

The straight-talking New Jersey's governor's presidential hopes largely ride on his confrontational style catching on -- particularly in New Hampshire, the state he's made the focus of his campaign.

But Trump's rise -- a new NBC News/Wall Street Journal poll out Sunday had the real estate mogul leading the Republican presidential field again with 19% support -- has dipped directly into Christie's potential well of support.

Now, Christie is landing around ninth place in national polls, putting him on the edge of missing the 10-person cutoff for Thursday's first GOP debate in Cleveland, hosted by Fox News.

That's fine with him, as long as he makes the cut, Christie said.

"Once you get on the stage it's not going matter whether you're number one or five or 10," he said. "You get the opportunity to make your pitch to the Republican primary voters across America."

He took another shot at Trump during the interview, calling his comment that undocumented immigrants should all be deported, with "the good ones" allowed back in an expedited process, as impractical as Trump's other proposal to build an enormous wall across the U.S.-Mexico border.

"This is like building a 2,000-mile wall across the border that Mexico's going to pay for," he said. "It sounds really good you, pound your chest, but the question is how? How are you going to do it?"

"Mission: Impossible - Rogue Nation" opened to an estimated $56 million at the U.S. box office over the weekend. This total was the second-best "Mission: Impossible" opening ever, just missing out on the $57.8 million of 2000's "Mission: Impossible II."

The Paramount film starring Tom Cruise was good enough to nab the third-best U.S. opening of the star's career, coming in behind "Mission: Impossible II" and 2005's "War of the Worlds."

The spy thriller was also a hit internationally. It made $65 million abroad to bring its global total to $121 million. A good start for a film that cost Paramount $150 million.

"Tom Cruise is the very definition of movie star, but beyond that he is a tireless marketing machine," said Paul Dergarabedian, a box office analyst for Rentrak. "He has essentially written the playbook on how to manifest the perfect combination of star-power based publicity along with producer-based business acumen."

Coming in at a distant second was Warner Bros.'s "Vacation" which earned $14.8 million between Friday and Sunday.

The comedy starring Ed Helms is the fifth installment of the "Vacation" franchise. Since opening on Wednesday, it has made $21.1 million for Warner Bros. (which, like CNN, is owned by Time Warner).

Two big films about small characters, Universal's "Minions" and Marvel's "Ant-Man," battled it out for third place. The $12.6 million of "Ant-Man" just edged out the $12.1 million of "Minions."

And to round out the top five was Sony's "Pixels" with $10.4 million. Box office sales for the Adam Sandler comedy dropped 57% from last week when it took second place.

As the summer box office season nears its end with next week's "Fantastic Four," Hollywood has a lot to be happy about. The 2015 summer box office is up 12.5% overall from last year.

President says plan is 'the biggest most important step we've ever taken to combat climate change'

The Obama administration will unveil a major climate change plan Monday aimed at a large reduction in greenhouse gas emissions from the nation's coal-burning power plants, a senior administration official told CNN.

President Barack Obama said Thursday night that he can feel some Democratic members of Congress getting "squishy" in their support of the Iran deal, bowing to the "political heat" they feel from the "fierce" lobbying campaign against the Iran deal.

The "Clean Power Plan" is the final version of regulations by the Environmental Protection Agency, which President Barack Obama called "the biggest most important step we've ever taken to combat climate change," in a video released by the White House on social media Saturday night.

The plan will call for a reduction power-sector carbon pollution of 32% from 2005 levels in 2030 -- a 9% increase over the 2014 draft proposal, the official said. It will also call for a more aggressive transition to renewable energy.

"Power plants are the single biggest source of harmful carbon pollution that contributes to climate change," Obama said in the video. "Until now, there have been no federal limits to the amount of carbon pollution plants dump in the air."

The plan, which will also include a requirement for states to submit their own respective plans, is already being met with major opposition from congressional Republicans and governors, including Wisconsin governor and presidential candidate Scott Walker.

Even before the rule was announced, many states announced plans to fight it, including some vows to take the administration to court over the new rules. Senate Majority Leader Mitch McConnell urged states not to comply with the plan in a letter to all 50 governors.

Critics also said that the plan will bring unwelcome increases in electricity prices.

"This plan is all pain and no gain," said Luke Popovich, vice president of communications for the National Mining Association. "That's why state leaders across the country are coming to the same conclusion -- that we should not sacrifice our power system to an unworkable plan built on a faulty interpretation of the law."

A multi-million dollar campaign backed by the energy industry has sought to debunk the science of climate change, but polls show most Americans believe the planet is warming.

Coal supplied 37% of U.S. electricity in 2012, compared to 30% from natural gas, 19% from nuclear power plants, 7% from hydropower sources such as dams and 5% from renewable sources such as wind and solar, according to the U.S. Energy Information Administration.

EPA officials have conceded in the past that some of the dirtiest power plants now operating, such as older coal-fired plants, will end up shuttered as the nation shifts its reliance from traditional fossil fuel sources to cleaner alternatives.

Expecting a tough fight, the White House will launch, what it describes as an "all-out climate push" by the President and cabinet officials to fan out to sell the plan. In the next several weeks, Obama will travel to Nevada to speak at the National Clean Energy Summit and later become the first sitting President to go to the Alaskan Arctic.

The impending battle ahead could be seen as a major legacy issue for Obama as he transitions into the last quarter of his presidency.

"There are few issues more important to the president," a senior administration official said, adding that Obama is likely to make the case that climate change is a moral, economic and national security obligation in the months ahead.

The news of the President's plan was hailed on Sunday by Democratic presidential candidates Hillary Clinton and Martin O'Malley.